How do you win the Silksong dice game? While it's entirely possible to win this little minigame with pure chance alone, a simple trick can guarantee you one easy win after the next. Whether or not the Silksong dice game rewards are worth it is entirely up to your particular playstyle, but you'll tick off a simple side quest regardless.
The Hollow Knight Silksong dice game is an optional activity in the Metroidvania that requires winning a game of chance enough times to take all of Lumble the Lucky's Rosaries. It's also the final stop before you face the Silksong Last Judge, so you can use your winnings to purchase additional items to help in the immediate future.
How to win the Silksong dice game
You can guarantee a Silksong dice game win by shaking the dice for exactly four seconds before rolling them. Rolling the dice outside of this perfect window results in a completely random outcome. As it should.

You can identify the perfect window for the dice game when the blue dice flash white, but relying on that alone demands very fast reflexes.
Instead, you can track Hornet's movements. She shakes the dice like a metronome; let go on the 14th shake for a guaranteed win. Hornet lets out a distinct sound whenever you're successful, which signals a winning roll.
Repeat this ten times in a row to clear Lumble's inventory. Remember that you can also just throw the dice at random for a chance to win regardless, though you might lose more rosaries than you gain in the process.
All dice game rewards
After you win the dice game ten times, Lumble rewards you with the Magnetite Dice. This is another hidden Silksong Tool that can be applied to your preferred Silksong Crest, giving you a random chance to negate an instance of damage. Alternatively, if you're not a fan of dice games, you can return later to retrieve the Magnetite Dice from Lumble's corpse. More on that below.

How to find the Silksong dice game
You can find Lumble the Lucky in Blasted Steps, between Bellhart and the Citadel.
The Blasted Steps is one of the most inhospitable places on the Silksong map, and just finding Lumble can be a challenge. To reach the area quickly, fast travel to Blasted Steps and head left and then down. Proceed left, leap over the Sandcarver pits, then continue until you reach Lumble the Lucky.

Aaron didn't get a chance to revel in the delights of the dice game in Act 1, so attempted to return to Lumble at the first chance they got to return to Blasted Steps in Act 2. However, as you can see in the screenshot above, he's very much dead. As noted above, the Magnetite Dice are still obtainable, and you'll find them nestled next to his corpse.

Some have reported that Lumble goes missing altogether if you attempt to return and play the dice game in Act 3. It's fairly safe to assume that his corpse has been swept away with the winds, Magnetite Dice and all. As it transpires, Grindle has nabbed them and, at this point, is selling them in his Blasted Steps store; the location of which you can see marked in the above screenshot.
The Silksong dice game is just one of many ways to pick up secret items in the indie game. Pick up the Silksong Simple Keys to get the most powerful ones early on, or watch out for the Silksong Pale Oil upgrade item to hit harder in the mid-game.